Stavudine (d4T) & didanosine (ddI) are nucleoside analogues with efficacy in adults; ddI is also efficacious in children; d4T is safe & has antiviral activity in children. With accumulating evidence suggesting that combination therapy may hold more promise than single- agent therapy in the long-term management of HIV infection, this study will evaluate the effect on plasma HIV RNA concentrations of d4T+ddI administered orally for 48 weeks. The safety & pharmacokinetic properties of the combination therapy also will be assessed.